The culture environment in which a mammalian cell is maintained can profoundly influence its state of differentiation and its longevity as well as its growth rate and productivity. Verax Corporation has developed a novel system for the mass culture of mammalian cells and has chosen large-scale production of monoclonal antibodies for its developmental work. The cell culture system utilizes a biomatrix, for the immobilization of cells, which is maintained during operation as a fluidized bed in a bioreactor of Verax design. The system is capable of continuous operation and has been run for months without interruption. The system is most productive when the cell density within the biomatrix is maximized. This application proposes three modifications of the biomatrix that will reduce the time it takes to reach this desired density and may result in achieving higher densities than are now observed. While this study will utilize hybridoma cells, the biomatrix modifications are not limited to this cell type.